Oil and Gas Terms Beginning with “R” — Page 3

A chemical added to an acid to stabilize iron. The injected acid dissolves iron from rust, millscale, iron scales or iron-containing minerals in the formation. Iron can exist as ferric iron [Fe+3] or ferrous iron… Read more →

A mound, ridge, or buildup of sediment or sedimentary rock, most commonly produced by organisms that secrete shells such as corals. Reefs are typically taller than the sediment that surrounds them, resistant to… Read more →

The device used to store and transport a coiled tubing string ready for use at the wellsite. The coiled tubing reel incorporates a manifold and swivel arrangement to enable fluids to be pumped through the coiled tubing… Read more →

The tension applied to a coiled tubing string as it passes between the reel and the injector head. An adequate back-tension must be maintained to ensure that the string spools correctly on or off the reel. Read more →

The position on a loggingtool string that is used as the reference for depth measurements. Each measurement has a different measure point. In normal practice, each measurement is shifted in depth by the distance between… Read more →

Generally, the return or rebound of particles or energy from the interface between two media. There are two laws of reflection, which state (1) that incident rays, reflected rays and the normal to the reflecting… Read more →

The ratio of amplitude of the reflected wave to the incident wave, or how much energy is reflected. If the wave has normal incidence, then its reflection coefficient can be expressed as:Typical values of R are… Read more →

A technique to measure and display the three-dimensional distribution of velocity or reflectivity of a volume of the Earth by using numerous sources and receivers at the Earth's surface. In reflection tomography, space… Read more →

An interface between layers of contrasting acoustic, optical or electromagnetic properties. Waves of electromagnetism, heat, light and sound can be reflected at such an interface. In seismic data, a reflector might… Read more →

The change in the direction of travel of a wavefront, or the bending of a ray, as it passes from one medium to another, expressed mathematically by Snell's law. Refraction is a consequence of changes in wavelength and… Read more →

The ratio of the speed of light in a vacuum to the speed of light in a given material, commonly symbolized by n. According to Snell's law, the refractive index is also the ratio of sine of the angle of incidence to the… Read more →

A layer of rock that is sufficiently thick, areally extensive, and has a distinctly higher velocity than the rocks immediately above it such that it can transmit a head wave, or a wave transmitted at its critical… Read more →

An operation to restimulate a well after an initial period of production. Refracturing operations attempt to bypass near-wellbore damage, reestablish good connectivity with the reservoir, and tap portions of the… Read more →

The statistical fitting of trend lines to a data set. Many regression methods are available, including linear, iterative, multiple and polynomial. If there is a 'good' fit to the data, then the variables are often… Read more →

A quantification of the degree of 'goodness' of fit of a regression line to a data set. A value of 0.5 represents random data with no dependence, and a coefficient of 1.0 represents a perfect fit with absolute… Read more →

The approximate age determination of rocks, fossils or minerals made by comparing whether the material is younger or older than other surrounding material. Relative age is estimated according to stratigraphic and… Read more →

The degree to which a medium resists the flow of electric charge divided by the degree to which free space resists such charge. The degree, or dielectric permittivity, is defined as the ratio of the electric… Read more →

Quantity that is double the filtrate volume collected from a filtration test between 7.5 to 30 minutes. This ignores the spurt of filtrate that comes out of the filter press before a cake is established. Relative… Read more →

The water content of air compared to the water content that the air could hold if it were saturated, expressed as a percentage. Air in equilibrium with fresh water is saturated with water vapor, so its RH = 100%. Air… Read more →

What Is Relative Permeability? Relative permeability (kr) is the ratio of effective permeability of a phase (oil, water, or gas) in a multiphase system to the absolute permeability of the rock at 100% saturation of that… Read more →

In a nuclear magnetic resonance (NMR) measurement, the characteristic time for a loss of coherent energy, or relaxation, by protons in rocks. There are two types of relaxation: longitudinal relaxation, which is the time… Read more →

A downhole tool that is designed to part under controlled conditions. A release joint enables part of the tool string to be left in the wellbore while the running string is retrieved. Read more →

The return of part or all of a lease or concession to a lessor, farmor or host government. The return may be voluntary or compelled contractually. Read more →

Cementing operations performed to repair primary-cementing problems or to treat conditions arising after the wellbore has been constructed. The two main categories of remedial cementing include squeeze cementing and the… Read more →

The process of measuring, observing or analyzing features of the Earth from a distance. Satellite photography and radar are techniques commonly used for remote sensing. Many geophysicists do not consider seismic methods… Read more →

An unmanned submersible vehicle controlled from surface. In deepwater operations, remotely operated vehicles are used to inspect subsea structures and equipment, and to control or manipulate valves. They can operate at… Read more →

An interval of log that has been recorded for a second time. The repeat section is typically 200 ft [60 m] long. The purpose is to judge the repeatability of the measurement by recording it twice over the same interval… Read more →

The quantitative value that is equal to or below the absolute difference between two test results, within a probability of 95%. (ISO)In a test of repeatability, the results are obtained independently by the normal and… Read more →

An acoustic velocity value used during processing to produce static, vertical shifts in seismic and other time domain data in order to bring a specific point into alignment with some common elevation feature. Most… Read more →

The quantitative value that is equal to or below the absolute difference between two test results obtained by operators in different laboratories, using the standard test method, within a probability of 95%. (ISO) Read more →